137 results found
Xiong Y, Tian T, L'Hermitte A, et al., 2022, Using silver exchange to achieve high uptake and selectivity for propylene/ propane separation in zeolite Y, Chemical Engineering Journal, Vol: 446, ISSN: 1385-8947
Adsorptive separation of propylene and propane, an important step of polypropylene production, is more energy-efficient than distillation. However, the challenge lies in the design of an adsorbent which exhibits both high selectivity and uptake. Herein, we hypothesise that enhancing the propylene affinity of the adsorption sites while keeping a suitable pore size can address this challenge. To do so, we performed silver exchange of a commercial zeolite Y, thereby making the adsorbent design easily scalable. We characterised the adsorbent using analytical, spectroscopic and imaging tools, tested its equilibrium and dynamic sorption properties using volumetric and gravimetric techniques and compared its performance to those of state-of-the-art adsorbents as well as other silver-functionalised adsorbents. The silver-exchanged zeolite Y (Ag-Y) exhibited one of the best selectivity vs uptake performances reported so far. Ag-Y also displayed fast adsorption kinetics and reversible propylene sorption, making it a promising new benchmark for propylene/propane separation. Synchrotron-based pair distribution function analyses identified the silver cations’ location which confirmed that the silver sites are easily accessible to the adsorbates. This aspect can, in part, explain the propylene/propane separation performance observed. The overall design strategy proposed here to enhance sorption site affinity and maintain pore size could be extended to other adsorbents and support the deployment of adsorption technology for propylene/propane separation.
Schukraft GEM, Itskou I, Woodward RT, et al., 2022, Evaluation of CO2 and H2O Adsorption on a Porous Polymer Using DFT and In Situ DRIFT Spectroscopy, JOURNAL OF PHYSICAL CHEMISTRY B, ISSN: 1520-6106
Tian T, Xu J, Xiong Y, et al., 2022, Cu-functionalised porous boron nitride derived from a metal–organic framework, Journal of Materials Chemistry A, Vol: 10, Pages: 20580-20592, ISSN: 2050-7488
Porous boron nitride (BN) displays promising properties for interfacial and bulk processes, e.g. molecular separation and storage, or (photo)catalysis. To maximise porous BN's potential in such applications, tuning and controlling its chemical and structural features is key. Functionalisation of porous BN with metal nanoparticle represents one possible route, albeit a hardly explored one. Metal–organic frameworks (MOFs) have been widely used as precursors to synthesise metal functionalised porous carbon-based materials, yet MOF-derived metal functionalised inorganic porous materials remain unexplored. Here, we hypothesise that MOFs could also serve as a platform to produce metal-functionalised porous BN. We have used a Cu-containing MOF, i.e. Cu/ZIF-8, as a precursor and successfully obtained porous BN functionalised with Cu nanoparticles (i.e. Cu/BN). While we have shown control of the Cu content, we have not yet demonstrated it for the nanoparticle size. The functionalisation has led to improved light harvesting and enhanced electron–hole separation, which have had a direct positive impact on the CO2 photoreduction activity (production formation rate 1.5 times higher than pristine BN and 12.5 times higher than g-C3N4). In addition, we have found that the metal in the MOF precursor impacts porous BN's purity. Unlike Cu/ZIF-8, a Co-containing ZIF-8 precursor led to porous C-BN (i.e. BN with a large amount of C in the structure). Overall, given the diversity of metals in MOFs, one could envision our approach as a method to produce a library of different metal functionalised porous BN samples.
Azzan H, Rajagopalan AK, L'Hermitte A, et al., 2022, Simultaneous estimation of gas adsorption equilibria and kinetics of individual shaped adsorbents, Chemistry of Materials, Vol: 34, Pages: 6671-6686, ISSN: 0897-4756
Shaped adsorbents (e.g., pellets, extrudates) are typically employed in several gas separation and sensing applications. The performance of these adsorbents is dictated by two key factors, their adsorption equilibrium capacity and kinetics. Often, adsorption equilibrium and textural properties are reported for materials. Adsorption kinetics are seldom presented due to the challenges associated with measuring them. The overarching goal of this work is to develop an approach to characterize the adsorption properties of individual shaped adsorbents with less than 100 mg of material. To this aim, we have developed an experimental dynamic sorption setup and complemented it with mathematical models, to describe the mass transport in the system. We embed these models into a derivative-free optimizer to predict model parameters for adsorption equilibrium and kinetics. We evaluate and independently validate the performance of our approach on three adsorbents that exhibit differences in their chemistry, synthesis, formulation, and textural properties. Further, we test the robustness of our mathematical framework using a digital twin. We show that the framework can rapidly (i.e., in a few hours) and quantitatively characterize adsorption properties at a milligram scale, making it suitable for the screening of novel porous materials.
Taddei M, Petit C, 2022, Engineering metal-organic frameworks for adsorption-based gas separations: from process to atomic scale (vol 6, pg 841, 2021), MOLECULAR SYSTEMS DESIGN & ENGINEERING, Vol: 7, Pages: 1162-1162, ISSN: 2058-9689
Xiao F-S, Azevedo D, Nicholas CP, et al., 2022, Preface for Special Issue on Engineered Methodologies for CO2 Utilization, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, Vol: 61, Pages: 10295-10297, ISSN: 0888-5885
Hwang J, Azzan H, Pini R, et al., 2022, H2, N2, CO2, and CH4 unary adsorption isotherm measurements at low and high pressures on zeolitic imidazolate framework ZIF-8, Journal of Chemical & Engineering Data, Vol: 67, Pages: 1674-1686, ISSN: 0021-9568
Excess adsorption of CO2, CH4, N2, and H2 on ZIF-8 was measured gravimetrically in the pressure range ranging from vacuum to 30 MPa at 298.15, 313.15, 333.15, 353.15, and 394.15 K using a magnetic suspension balance. The textural properties of the adsorbent material─i.e., skeletal density, surface area, pore volume, and pore-size distribution─were estimated by helium gravimetry and N2 (77 K) physisorption. The adsorption isotherms were fitted with the Sips isotherm model and the virial equation, and the values of isosteric heat of adsorption and Henry constants for the gases were determined using the latter.
Osterrieth JWM, Rampersad J, Madden D, et al., 2022, How Reproducible are Surface Areas Calculated from the BET Equation?, ADVANCED MATERIALS, Vol: 34, ISSN: 0935-9648
Shankar RB, Mistry EDR, Lubert-Perquel D, et al., 2022, A response surface model to predict and experimentally tune the chemical, magnetic and optoelectronic properties of oxygen-doped boron nitride, ChemPhysChem: a European journal of chemical physics and physical chemistry, Vol: 23, ISSN: 1439-4235
Porous boron nitride (BN), a combination of hexagonal, turbostratic and amorphous BN, has emerged as a new platform photocatalyst. Yet, this material lacks photoactivity under visible light. Theoretical studies predict that tuning the oxygen content in oxygen-doped BN (BNO) could lower the band gap. This is yet to be verified experimentally. We present herein a systematic experimental route to simultaneously tune BNO's chemical, magnetic and optoelectronic properties using a multivariate synthesis parameter space. We report deep visible range band gaps (1.50–2.90 eV) and tuning of the oxygen (2–14 at.%) and specific paramagnetic OB3 contents (7–294 a.u. g−1). Through designing a response surface via a design of experiments (DOE) process, we have identified synthesis parameters influencing BNO's chemical, magnetic and optoelectronic properties. We also present model prediction equations relating these properties to the synthesis parameter space that we have validated experimentally. This methodology can help tailor and optimise BN materials for heterogeneous photocatalysis.
Schukraft GEM, Moss B, Kafizas AG, et al., 2022, Effect of band bending in photoactive MOF-based heterojunctions., ACS Applied Materials and Interfaces, Vol: 14, Pages: 19342-19352, ISSN: 1944-8244
Semiconductor/metal-organic framework (MOF) heterojunctions have demonstrated promising performance for the photoconversion of CO2 into value-added chemicals. To further improve performance, we must understand better the factors which govern charge transfer across the heterojunction interface. However, the effects of interfacial electric fields, which can drive or hinder electron flow, are not commonly investigated in MOF-based heterojunctions. In this study, we highlight the importance of interfacial band bending using two carbon nitride/MOF heterojunctions with either Co-ZIF-L or Ti-MIL-125-NH2. Direct measurement of the electronic structures using X-ray photoelectron spectroscopy (XPS), work function, valence band, and band gap measurements led to the construction of a simple band model at the heterojunction interface. This model, based on the heterojunction components and band bending, enabled us to rationalize the photocatalytic enhancements and losses observed in MOF-based heterojunctions. Using the insight gained from a promising band bending diagram, we developed a Type II carbon nitride/MOF heterojunction with a 2-fold enhanced CO2 photoreduction activity compared to the physical mixture.
Heiba HF, Bullen JC, Kafizas A, et al., 2022, The determination of oxidation rates and quantum yields during the photocatalytic oxidation of As(III) over TiO2, Journal of Photochemistry and Photobiology A: Chemistry, Vol: 424, Pages: 113628-113628, ISSN: 1010-6030
The determination of reaction rates for the photocatalytic oxidation (PCO) of arsenite (As(III)) using TiO2 under UV radiation is challenging due to the numerous experimental processes. This includes chemical processes running simultaneously with PCO (e.g. adsorption of arsenic species, direct UV photolysis of As(III)) and the analytical approach used (e.g. whether As(III) or As(V) are measured and used in the calculation of the PCO rate). The various experimental approaches used to date have led to oxidation rates and rate constants which vary by orders of magnitude and contradicting information on rate laws. Here we present the results of a critical examination of possible controls affecting the experimental determination of PCO rates. First, we demonstrate that the choice of analytical technique is not critical, provided that the rate constants are calculated based on the depletion of As(III) after correction of the directly adsorbed As(III). Second, we show the correction of the directly adsorbed As(III) at each time interval is best done by running two parallel experiments (one under UV and the other in dark) instead of running sequential experiment (i.e. running the experiment in the dark then turning on the UV lamp). These findings are supported by XPS analysis of the oxidation state of TiO2-sorbed As. Third, we demonstrate that photolysis by the light source itself, as well as the chemical composition of the solution (i.e. the effect of HEPES and the ionic strength), can significantly increase As(III) oxidation rates and need to be corrected. Finally, to determine the quantum yield of As(III) oxidation, we measured the photon absorption by the TiO2 photocatalyst. Our results showed that the quantum yield (Ø) for this oxidation reaction was low, and in the region of 0.1 to 0.2 %.
Petit C, L'Hermitte A, Dawson D, et al., 2021, Formation mechanism and porosity development in porous boron nitride, The Journal of Physical Chemistry C: Energy Conversion and Storage, Optical and Electronic Devices, Interfaces, Nanomaterials, and Hard Matter, Vol: 125, Pages: 27429-27439, ISSN: 1932-7447
Porous boron nitride (BN) has proven promising as a novel class of inorganic materials in the field of separations and particularly adsorption. Owing to its high surface area and thermal stability, porous BN has been researched for CO2 capture and water cleaning, for instance. However, research remains at the laboratory scale due to a lack of understanding of the formation mechanism of porous BN, which is largely a “black box” and prevents scale up. Partial reaction pathways have been unveiled, but they omit critical steps in the formation, including the porosity development, which is key to adsorption. To unlock the potential of porous BN at a larger scale, we have investigated its formation from the perspective of both chemical formation and porosity development. We have characterized reaction intermediates obtained at different temperatures with a range of analytical and spectroscopic tools. Using these analyses, we propose a mechanism highlighting the key stages of BN formation, including intermediates and gaseous species formed in the process. We identified the crucial formation of nonporous carbon nitride to form porous BN with release of porogens, such as CO2. This work paves the way for the use of porous BN at an industrial level for gas and liquid separations.
Rajagopalan AK, Petit C, 2021, Material Screening for Gas Sensing Using an Electronic Nose: Gas Sorption Thermodynamic and Kinetic Considerations, ACS SENSORS, Vol: 6, Pages: 3808-3821, ISSN: 2379-3694
Butler EL, Reid B, Luckham PF, et al., 2021, Interparticle Forces of a Native and Encapsulated Metal-Organic Framework and Their Effects on Colloidal Dispersion, ACS APPLIED MATERIALS & INTERFACES, Vol: 13, Pages: 45898-45906, ISSN: 1944-8244
Taddei M, Petit C, 2021, Engineering metal-organic frameworks for adsorption-based gas separations: from process to atomic scale, Molecular Systems Design & Engineering, Vol: 6, Pages: 841-875, ISSN: 2058-9689
Metal-organic frameworks (MOFs) are the object of intense research targeting their deployment as adsorbents for a wide range of gas separations, such as CO2 capture, biogas upgrading, air separation and small hydrocarbons separation. The scope of this review is to provide chemists, material scientists and engineers with an overview of the state-of-the-art and of the main challenges in the field of adsorption-based gas separations using MOFs. To do so, we first discuss current gas separation challenges for which adsorption could play a role. The following three sections of the paper describe process-level considerations in the design, selection and deployment of MOFs as sorbents and subsequently focus on material-level considerations. Both the process and the material aspects cover experimental and computational work. Going from the process scale to the atomic scale, we aim to highlight the links and synergies between the two and identify the current barriers that hamper the development of adsorption-based gas separations using MOFs as sorbents. Throughout the article, we also provide fundamental and technical information related to MOFs design, synthesis, characterisation and sorption testing.
Xiong Y, Woodward RT, Danaci D, et al., 2021, Understanding trade-offs in adsorption capacity, selectivity and kinetics for propylene/propane separation using composites of activated carbon and hypercrosslinked polymer, CHEMICAL ENGINEERING JOURNAL, Vol: 426, ISSN: 1385-8947
Rampal N, Ajenifuja A, Tao A, et al., 2021, The development of a comprehensive toolbox based on multi-level, high-throughput screening of MOFs for CO/N-2 separations, CHEMICAL SCIENCE, Vol: 12, Pages: 12068-12081, ISSN: 2041-6520
Danaci D, Bui M, Petit C, et al., 2021, En route to zerio emissions for power and industry with amine-based post-combustion capture, Environmental Science and Technology (Washington), Vol: 55, Pages: 10619-10632, ISSN: 0013-936X
As more countries commit to a net-zero GHG emission target, we need a whole energy and industrial system approach to decarbonization rather than focus on individual emitters. This paper presents a techno-economic analysis of monoethanolamine-based post-combustion capture to explore opportunities over a diverse range of power and industrial applications. The following ranges were investigated: feed gas flow rate between 1–1000 kg ·s–1, gas CO2 concentrations of 2–42%mol, capture rates of 70–99%, and interest rates of 2–20%. The economies of scale are evident when the flue gas flow rate is <20 kg ·s–1 and gas concentration is below 20%mol CO2. In most cases, increasing the capture rate from 90 to 95% has a negligible impact on capture cost, thereby reducing CO2 emissions at virtually no additional cost. The majority of the investigated space has an operating cost fraction above 50%. In these instances, reducing the cost of capital (i.e., interest rate) has a minor impact on the capture cost. Instead, it would be more beneficial to reduce steam requirements. We also provide a surrogate model which can evaluate capture cost from inputs of the gas flow rate, CO2 composition, capture rate, interest rate, steam cost, and electricity cost.
Tian T, Hou J, Ansari H, et al., 2021, Mechanically stable structured porous boron nitride with high volumetric adsorption capacity, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 9, Pages: 13366-13373, ISSN: 2050-7488
Schukraft GEM, Woodward RT, Kumar S, et al., 2021, Hypercrosslinked polymers as a photocatalytic platform for visible-light-driven CO2 photoreduction using H2O, ChemSusChem: chemistry and sustainability, energy and materials, Vol: 14, Pages: 1720-1727, ISSN: 1864-5631
The design of robust, high‐performance photocatalysts is key for the success of solar fuel production by CO2 conversion. In this study, hypercrosslinked polymer (HCP) photocatalysts have been developed for the selective reduction of CO2 to CO, combining excellent CO2 sorption capacities, good general stabilities, and low production costs. HCPs are active photocatalysts in the visible light range, significantly outperforming the benchmark material, TiO2 P25, using only sacrificial H2O. It is hypothesized that superior H2O adsorption capacities facilitate access to photoactive sites, improving photocatalytic conversion rates when compared to sacrificial H2. These polymers are an intriguing set of organic photocatalysts, displaying no long‐range order or extended π‐conjugation. The as‐synthesized networks are the sole photocatalytic component, requiring no added cocatalyst doping or photosensitizer, representing a highly versatile and exciting platform for solar‐energy conversion.
Stafford J, Uzo N, Farooq U, et al., 2021, Real-time monitoring and hydrodynamic scaling of shear exfoliated graphene, 2D Materials, Vol: 8, Pages: 1-17, ISSN: 2053-1583
Shear-assisted liquid exfoliation is a primary candidate for producing defect-free two-dimensional (2D) materials. A range of approaches that delaminate nanosheets from layered precursors in solution have emerged in recent years. Diverse hydrodynamic conditions exist across these methods, and combined with low-throughput, high-cost characterization techniques, strongly contribute to the wide variability in performance and material quality. Nanosheet concentration and production rate are usually correlated against operating parameters unique to each production method, making it difficult to compare, optimize and predict scale-up performance. Here, we reveal the shear exfoliation mechanism from precursor to 2D material and extract the derived hydrodynamic parameters and scaling relationship that are key to nanomaterial output and common to all shear exfoliation processes. Our investigations use conditions created from two different hydrodynamic instabilities—Taylor vortices and interfacial waves—and combine materials characterization, fluid dynamics experiments and numerical simulations. Using graphene as the prototypical 2D material, we find that scaling of concentration of few-layer nanosheets depends on local strain rate distribution, relationship to the critical exfoliation criterion, and precursor residence time. We report a transmission-reflectance method to measure concentration profiles in real-time, using low-cost optoelectronics and without the need to remove the layered precursor material from the dispersion. We show that our high-throughput, in situ approach has broad uses by controlling the number of atomic layers on-the-fly, rapidly optimizing green solvent design to maximize yield, and viewing live production rates. Combining the findings on the hydrodynamics of exfoliation with this monitoring technique, we unlock targeted process intensification, quality control, batch traceability and individually customizable 2D materials on-demand.
Danaci D, Webley PA, Petit C, 2021, Guidelines for techno-economic analysis of adsorption processes, Frontiers in Chemical Engineering, Vol: 2, ISSN: 2673-2718
Techno-economic analyses (TEAs) of CO2 capture technologies have risen in popularity, due to growing interest in meeting CO2 emissions reduction targets. Adsorption processes are one of the technologies proposed for CO2 capture, and although difficult, standardisation of TEAs for adsorption should be attempted. The reason is that TEAs are often referred to as input data to other forms of modelling, to guide policy, and act as summaries for those unfamiliar with adsorption processes. Herein, we discuss the aspects that should be considered when conducting TEAs for CO2 adsorption processes, we present the implications of choices made at the TEA stage and offer guidance on best practice. Overall, our aim is to make TEAs of adsorption processes more widely accessible to the adsorption community, and also more generally to communities engaged in the evaluation of CCS technologies.
Farooq U, Stafford J, Petit C, et al., 2020, Numerical simulations of a falling film on the inner surface of a rotating cylinder, Physical Review E, Vol: 102, Pages: 043106 – 1-043106 – 13, ISSN: 2470-0045
A flow in which a thin film falls due to gravity on the inner surface of a vertical, rotating cylinder is investigated. This is performed using two-dimensional (2D) and 3D direct numerical simulations, with a volume-of-fluid approach to treat the interface. The problem is parameterized by the Reynolds, Froude, Weber, and Ekman numbers. The variation of the Ekman number (Ek), defined to be proportional to the rotational speed of the cylinder, has a strong effect on the flow characteristics. Simulations are conducted over a wide range of Ek values (0≤Ek≤484) in order to provide detailed insight into how this parameter influences the flow. Our results indicate that increasing Ek, which leads to a rise in the magnitude of centrifugal forces, produces a stabilizing effect, suppressing wave formation. Key flow features, such as the transition from a 2D to a more complex 3D wave regime, are influenced significantly by this stabilization and are investigated in detail. Furthermore, the imposed rotation results in distinct flow characteristics such as the development of angled waves, which arise due to the combination of gravitationally and centrifugally driven motion in the axial and azimuthal directions, respectively. We also use a weighted residuals integral boundary layer method to determine a boundary in the space of Reynolds and Ekman numbers that represents a threshold beyond which waves have recirculation regions.
Ye Z, Schukraft GEM, L'Hermitte A, et al., 2020, Mechanism and stability of an Fe-based 2D MOF during the photoelectro-Fenton treatment of organic micropollutants under UVA and visible light irradiation, WATER RESEARCH, Vol: 184, ISSN: 0043-1354
Butler EL, Petit C, Livingston AG, 2020, Poly(piperazine trimesamide) thin film nanocomposite membrane formation based on MIL-101: Filler aggregation and interfacial polymerization dynamics, JOURNAL OF MEMBRANE SCIENCE, Vol: 596, ISSN: 0376-7388
Evans A, Cummings M, Decarolis D, et al., 2020, Optimisation of Cu+ impregnation of MOF-74 to improve CO/N2 and CO/CO2 separations, RSC Advances: an international journal to further the chemical sciences, Vol: 10, Pages: 5152-5162, ISSN: 2046-2069
Carbon monoxide (CO) purification from syngas impurities is a highly energy and cost intensive process. Adsorption separation using metal–organic frameworks (MOFs) is being explored as an alternative technology for CO/nitrogen (N2) and CO/carbon dioxide (CO2) separation. Currently, MOFs' uptake and selectivity levels do not justify displacement of the current commercially available technologies. Herein, we have impregnated a leading MOF candidate for CO purification, i.e. M-MOF-74 (M = Co or Ni), with Cu+ sites. Cu+ allows strong π-complexation from the 3d electrons with CO, potentially enhancing the separation performance. We have optimised the Cu loading procedure and confirmed the presence of the Cu+ sites using X-ray absorption fine structure analysis (XAFS). In situ XAFS and diffuse reflectance infrared Fourier Transform spectroscopy analyses have demonstrated Cu+–CO binding. The dynamic breakthrough measurements showed an improvement in CO/N2 and CO/CO2 separations upon Cu impregnation. This is because Cu sites do not block the MOF metal sites but rather increase the number of sites available for interactions with CO, and decrease the surface area/porosity available for adsorption of the lighter component.
Danaci D, Bui M, Mac Dowell N, et al., 2020, Exploring the limits of adsorption-based CO2 capture using MOFs with PVSA – from molecular design to process economics, Molecular Systems Design and Engineering, Vol: 5, Pages: 212-231, ISSN: 2058-9689
Metal-organic frameworks (MOFs) have taken the materials science world by storm, with potentials of near infinite possibilities and the panacea for adsorption-based carbon capture. Yet, no pilot-scale (or larger-scale) study exists on MOFs for carbon capture. Beyond material scalability issues, this clear gap between the scientific and engineering literature relates to the absence of suitable and accessible assessment of MOFs in an adsorption process. Here, we have developed a simple adsorbent screening tool with process economics to evaluate adsorbents for post-combustion capture, while also considering factors relevant to industry. Specifically, we have assessed the 25 adsorbents (22 MOFs, 2 zeolites, 1 activated carbon) against performance constraints – i.e. CO2 purity and recovery – and cost. We have considered four different CO2 capture scenarios to represent a range of CO2 inlet concentrations. The cost is compared to that of amine-based solvents for which a corresponding model was developed. Using the model developed, we have conceptually assessed the materials properties and process parameters influencing the purity, recovery and cost in order to design the ‘best’ adsorbent. We have also set-up a tool for readers to screen their own adsorbent. In this contribution, we show that minimal N2 adsorption and moderate enthalpies of adsorption are key in obtaining good process performance and reducing cost. This stands in contrast to the popular approaches of maximizing CO2 capacity or surface area. Of the 22 MOFs evaluated, UTSA-16 shows the best performance and lowest cost for post-combustion capture, having performance in-line with the benchmark, zeolite 13X. Mg-MOF-74 performs poorly. The cost of using the adsorbents remains overall higher than that of an amine-based absorption process. Ultimately, this study provides specific directions for material scientists to design adsorbents and assess their performance at the process scale. This
Thompson JF, Bellerjeau C, Marinick G, et al., 2019, Intrinsic Thermal Desorption in a 3D Printed Multifunctional Composite CO2 Sorbent with Embedded Heating Capability, ACS APPLIED MATERIALS & INTERFACES, Vol: 11, Pages: 43337-43343, ISSN: 1944-8244
Shankar R, Sachs M, Francas L, et al., 2019, Porous boron nitride for combined CO2 capture and photoreduction, Journal of Materials Chemistry A, Vol: 7, Pages: 23931-23940, ISSN: 2050-7488
Porous and amorphous materials are typically not employed for photocatalytic purposes, like CO2 photoreduction, as their high number of defects can lead to low charge mobility and favour bulk electron–hole recombination. Yet, with a disordered nature can come porosity, which in turn promotes catalyst/reactant interactions and fast charge transfer to reactants. Here, we demonstrate that moving from h-BN, a well-known crystalline insulator, to amorphous BN, we create a semiconductor, which is able to photoreduce CO2 in the gas/solid phase, under both UV-vis and pure visible light and ambient conditions, without the need for cocatalysts. The material selectively produces CO and maintains its photocatalytic stability over several catalytic cycles. The performance of this un-optimized material is on par with that of TiO2, the benchmark in the field. For the first time, we map out experimentally the band edges of porous BN on the absolute energy scale vs. vacuum to provide fundamental insight into the reaction mechanism. Owing to the chemical and structural tunability of porous BN, these findings highlight the potential of porous BN-based structures for photocatalysis particularly solar fuel production.
Evans AD, Cummings MS, Luebke R, et al., 2019, Screening metal–organic frameworks for dynamic CO/N2 separation using complementary adsorption measurement techniques, Industrial & Engineering Chemistry Research, Vol: 58, Pages: 18336-18344, ISSN: 0888-5885
Carbon monoxide (CO)/nitrogen (N2) separation is a particularly challenging separation, yet it is the one with great industrial relevance for its use in petrochemical synthesis. Although an expensive cryogenic step can be used to perform such separation, it remains ineffective in purifying CO from syngas streams with a significant N2 content. Taking advantage of the lower energy requirement of adsorption processes, we have explored the use of metal–organic frameworks (MOFs) as adsorbents for this difficult separation. We have screened a range of MOF candidates for CO/N2 separation covering a range of chemical and textural features, using the flux response technology to evaluate their dynamic performance for throughput testing alongside equilibrium uptake measurements. We have identified Ni-MOF-74 and Co-MOF-74 as the most promising candidates because of their high metal density and strong metal–CO interactions. We have investigated further the effect of N2 impurity concentrations upon CO/N2 separation using breakthrough adsorption testing and cyclic testing (up to 20 cycles). Overall, using multiple adsorption measurement techniques, this study demonstrates the CO/N2 dynamic separation performance of M-MOF-74 and its ability to be applied for an industrially relevant separation.
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